The Effect of Dried Plum on Serum Levels of Receptor Activator of NF-kB Ligand, Osteoprotegerin and Sclerostin in Osteopenic Postmenopausal Women: A Randomised Controlled Trial

The mechanisms by which dried plums impart bone-protective properties remain unclear. Recent research has shown that osteocytes may control bone formation via the production of sclerostin and bone resorption via the receptor activator of NF-kB ligand (RANKL) and its inhibitor osteoprotegerin (OPG). In this study, the researchers measured serum levels of RANKL, OPG and sclerostin in osteopenic postmenopausal women (n 160) to investigate the mechanism of action of dried plum in reversing bone loss.

Participants were randomly assigned to the treatment group of either 100 g dried plum/d or 75 g dried apple/d (comparative control) for 1 year (Previously reported in “Comparative Effects of Dried Plum and Dried Apple on Bone in Postmenopausal Women”). All participants received 500mg Ca plus 400 IU (10 mg) vitamin D daily. Bone mineral densities (BMD) of the lumbar spine, forearm, hip and whole body were assessed at baseline and at the end of the study using dual-energy X-ray absorptiometry. Blood samples were collected at baseline and after 12 months to assess bone biomarkers. Dried plum significantly increased the BMD of the ulna and spine in comparison with the control group. In comparison with corresponding baseline values, dried plum increased the RANKL levels by only +1.99 v. +18.33% and increased the OPG levels by +4.87 v.-2.15% in the control group. Serum sclerostin levels were reduced by -1.12% in the dried plum group v. +3.78% in the control group. Although percentage changes did not reach statistical significance (P <0•05), these preliminary data may indicate that the positive effects of dried plum on bone are in part due to the suppression of RANKL production, the promotion of OPG and the inhibition of sclerostin.

Comparative Effects of Dried Plum and Dried Apple on Bone in Postmenopausal Women

This study examined the extent to which dried plum reverses bone loss in osteopenic postmenopausal women. Participants were 1-10 years postmenopausal and not on hormone replacement therapy or other prescribed medication known to influence bone metabolism. Qualified participants (n 160) were randomly assigned to one of two treatment groups: dried plum (100g/d) or dried apple (comparative control). Participants also received 500 mg calcium and 400 IU vitamin D daily. Bone mineral density (BMD) of lumbar spine, forearm, hip and whole body was assessed at baseline and at the end of the study using dual-energy X-ray absorptiometry. Blood samples collected at baseline, 3,6, and 12 months assessed bone biomarkers. Physical activity recall and 1-week-food frequency questionnaires were obtained at baseline, 3,6, and 12 months to examine physical activity and dietary confounders as potential covariates.

Dried plum significantly increased BMD of ulna and spine compared to dried apple. Compared to corresponding baseline values, only dried plum significantly decreased serum levels of bone turnover markers including bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase-5b. The authors maintain that the findings confirmed the ability of dried plum to imporve BMD in postmenopausal women in part due to suppressing the rate of bone turnover.

This study compared the effects of dried plum on bone to other dried fruits (apple, apricot, grape or mango) and further explored the potential mechanisms of action by which dried plum may exert its osteoprotective effects. Adult osteopenic ovariectomized (OVX) mice were fed a control diet or diet supplemented with 25% (w/w) dried fruit for 8 weeks. Whole body and spine bone mineral density improved in mice fed the dried plum, apricot and grape diets compared to the OVX control; but only dried plum had an anabolic effect on trabecular bone in the vertebra and prevented bone loss in the tibia. Restoration of biomechanical properties occurred along with the changes in trabecular bone in the spine. According to the researchers, compared to other dried fruits in this study, dried plum was unique in its ability to down-regulate osteoclast differentiation while up-regulating osteoblast and glutathione activities. These alternations in bone metabolism and antioxidant status compared to other dried fruits provide some insight into dried plum’s unique effects on bone.

Dried Plum Restores Bone in Aging Mice

J. Nutr. October 1, 2010 vol. 140 no. 10 1781-1787.Halloran BP et al.

Therapies to prevent or restore bone progessively lost with advancing age are limited. The only effective proanabolic regimen presently available to restore bone is intermittent treatment with teriparatide (parathyroid hormone 1–34). Previous studies suggest that dietary supplementation with dried plum (DP) can prevent bone loss due to estrogen deficiency. This study was undertaken to investigate whether dietary DP supplementation can prevent the loss of bone with aging and whether bone that has already been lost can be restored in an animal model. Adult (6 mo) and old (18 mo) male mice were fed a normal diet or isoenergetic, isonitrogenous diets supplemented with DP (0, 15, and 25% DP by weight) for 6 mo. MicroCT analysis and bone histomorphometry assessed bone volume, structure, and metabolic activity before, during, and after dietary supplementation. The researchers report that mice fed the 0% DP diet (control diet) lost bone, whereas both adult and old mice fed the 25% DP-supplemented diet gained bone. Adult but not old mice fed the 15% diet also gained bone. Cancellous bone volume in mice receiving 25% DP exceeded baseline levels by 40–50%. Trabecular structure varied with diet and age and responses in old mice were generally blunted. Trabecular, but not cortical, mineral density varied with age and measures of bone anabolic activity were lower in aged mice. Findings suggest that DP contains proanabolic factors that can dramatically increase bone volume and restore bone that has already been lost due to aging. In turn, DP may provide effective prophylactic and therapeutic agents for the treatment of osteoporosis.

Dried Plum Polyphenols Inhibit Osteoclastogenesis

This study investigated dried plum polyphenols' effect on osteoclast differentiation and activity in cell cultures. Results of this study, combined with results of the authors' previous reports, suggest that the antiresorptive properties of dried plums observed in animal studies are in part mediated by polyphenols suppression of osteoclast differentiation and activity under normal, oxidative stress, and inflammatory conditions.

The study was designed to determine the extent to which dried plum prevents skeletal deterioration in gonadal hormone deficient male animals and to begin to understand the mechanism. Sham operated on orchidectomized male rats fed dried plum diets at 5, 15 and 25 percent (w/w) levels. The 15 and 25 percent dried plum diets prevented the ORX-induced decrease in whole body, femur and lumbar vertebrae bone mineral density. Results of other biomechanical testing are discussed. The authors conclude that dried plum prevents osteopenia in androgen deficient male rats and that the benefits may be attributed in part to a decrease in osteoclastogenesis via down-regulation of the RANKl and stimulation of bone formation mediated by IGF-I.

DP Prevents Bone Loss in an Osteopenic Rat Model of Osteoporosis

This study evaluated whether dried plum was able to restore bone mass in osteopenic ovariectomized rats. Dried plum at 5% of the diet was effective in restoring femoral and tibial bone density and increased lumbar bone density. The increase in femoral bone density in rats fed dried plum diets resulted in improved bone quality as indicated by 6.9% and 6.0% improvement in overall yield and ultimate force respectively. The improvement in biomechanical properties of long bones due to dried plum, in part, may be due to the favorable microstructural changes as evident by enhanced tibial bone volume and connectivity.

Dried Plums Improve Indices of Bone Formation in Postmenopausal Women

The study assessed the effect of daily consumption of 100 grams (10–12) of dried plums for three months on markers of bone turnover. Compared to baseline, dried plums significantly increased serum levels of IGF-I and BSAP activity. According to the authors, higher levels are associated with greater rates of bone formation.

This review summarizes findings of studies published to date which examine the beneficial effects of dried plum on bone in both female and male animals models of osteoporosis as well as a published clinical trial. Animal studies indicate that dried plum protects against but more importantly reverses bone loss in two separate models of osteopenia. A 3-month clincial trial indicated that consumption of dried plum daily by postmenopausal women significantly increased serum markers of bone formation, total alkaline phosphatase, bone-specific alkaline phosphatase and insulin-like growth factor-1 by 12, 6, and 17% respectively.